Protective helmet



FIG. 1 is a right-side view of a protective helmet showing our new design;

FIG. 2 is a left-side view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a top view thereof;

FIG. 6 is a bottom view thereof;

FIG. 7 is a top, front and right-side perspective view thereof;

FIG. 8 is a bottom, rear and left-side perspective view thereof; and,

FIG. 9 is another right-side view thereof, the only difference residing in the removal of the broken line detail on the face shield in FIG. 1.

The details shown in FIGS. 1-9 form no part of the claimed design. 

We claim the ornamental design for a protective helmet, as shown and described. 